border-1px($color)
  position: relative;
  &:after
    display: block;
    position: absolute;
    left: 0px;
    bottom: 0px;
    width:100%;
    border-top: 1px solid $color;
    content: '';

border-none()
&:after
 display:none;

bg-image($url)
    background-image: url($url+"@2x.png");
  @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3)
    background-image: url($url+"@3x.png");
